Objectively-assessed physical activity and heat stress and the association with kidney function in female harvest workers in Spain

Abstract

BACKGROUND AND AIM: Physical activity (PA) in hot environments has been associated with kidney damage. In harvest workers, PA has been primarily assessed by questionnaires in males. We aimed to study the association between objectively-measured PA intensity and incidence of acute kidney injury (AKI) over the course of one work shift, in female harvest workers in Spain. METHODS: Ninety women working in greenhouses wore a Zephyr chest harness to measure PA intensity during one regular work shift in June 2020. We determined the mean (PA_mean), standard deviation (PA_sd), and 3-minute-maximum (PA_max, a proxy of peak PA intensity) of PA intensity (vector magnitude units). We estimated heat stress (HS) in greenhouses based on wet bulb globe temperature index (ISO 7243:2017). Serum creatinine and neutrophil gelatinase associated lipocalin (NGAL) levels were measured before and after the work shift. AKI was defined as an increase in post-shift serum creatinine by at least 0.3 mg/dl or at least 1.5 times the pre-shift serum creatinine levels. Additionally, we calculated pre-post-shift differences in NGAL. We used logistic regressions adjusted for age, body mass index, and HS. HS was also assessed as an effect modifier. RESULTS: PA_sd and PA_max seemed to be associated with AKI (OR=1.57 (95%CI=0.82;3.21) and 1.41 (0.71;2.85), respectively), but not PA_mean. There was no interaction between any of the PA variables and HS (p-value LRT>0.1). Mean (SD) increase in NGAL levels over the course of a work shift was higher among participants with AKI (27.8 (7.5)) compared to those without AKI (12.2 (2.7)). CONCLUSIONS: Results suggest that large changes and peaks in PA intensity should be avoided to protect renal function of harvest workers. Increased levels of NGAL among those with AKI are indicative of kidney damage among those with increased serum creatinine levels. KEYWORDS: Occupational physical activity, acute kidney injury, ambient heat stress